1. Field of the Invention
The present invention relates to a silicon wafer cleaning method.
Priority is claimed on Japanese Patent Application No. 2005-231430, filed Aug. 10, 2005, the content of which is incorporated herein by reference.
2. Description of the Related Art
In mirror-polishing of silicon wafers, the surface of a silicon wafer mounted on a holding jig is pressed with prescribed pressure against a polishing cloth fixed onto a turntable, and by rotating the turntable while supplying a polishing slurry between the polishing cloth and the wafer surface, the wafer surface is polished to a mirror finish. As the polishing slurry, normally a liquid prepared by suspending fine SiO2 particles or other abrasive particles in a weak alkaline liquid is used; cellulose or other polymer components may be further added to reduce haze and LPD, or to maintain wettability.
After mirror-polishing, a silicon wafer is cleaned in order to remove particles, organic contaminants, metallic impurities and other contaminants which may exist on the surface. In general, the RCA method is used to clean silicon wafers after mirror polishing has been completed (see for example Non-Patent Reference 1: Fumio Shimura, Handoutai Shirikon Kesshougaku, Maruzen, Sep. 30, 1993, pp. 125-127). The RCA method comprises two-stage cleaning using (1) a high-pH alkaline liquid mixture (hereafter “SC-1”) based on hydrogen peroxide, and (2) a low-pH acidic liquid mixture (hereafter “SC-2”). By combining these liquid mixtures to perform cleaning, contaminants can be efficiently removed from the substrate surface.
However, polymer components contained in the polishing slurry used in mirror polishing remain on the surface of a silicon wafer after the completion of mirror polishing, and when using the RCA cleaning described in the above Non-Patent Reference 1, the polymer component contained in the polishing slurry undergoes a dehydration condensation or other reaction due to the SC-1 liquid mixture, to form derivatives of the polymer component; because this derivative is fixed on the wafer surface, the derivative fixed on the wafer surface is not removed even when SC-2 cleaning is performed following SC-1 cleaning, and so the cleanliness of the wafer surface cannot be improved sufficiently.